Experiments were performed to investigate perceptual contributions of static and dynamic features of vocal tract characteristics to talker individuality. An ARX (Auto-regressive with exogenous input) speech production model was used to extract separately voice source and vocal tract parameters from a Japanese sentence, /aoiueoie/ ("Say blue top" in English) uttered by three males. The Discrete Cosine Transform (DCT) was applied to resolve formant trajectories of the speech signal into static and dynamic components. The perceptual contributions were quantitatively studied by systematically replacing the corresponding formant components of the sentences between the three talkers. Results of the experiments show that the static (average) feature of the vocal tract is a primary cue to talker individuality.